Event-triggered strategies for the networked control of freeway traffic systems

In this paper event-triggered model predictive schemes for the networked control of freeway traffic systems via ramp metering are proposed, with the final aim of reducing both the computational and the communication effort. When in traffic control systems the communication between the sensors and the controller occurs through a shared digital communication network, this latter can be affected by network delays and packet dropouts, which tend to increase with the network overload. For this reason, it is important to devise traffic control strategies which, apart from being applicable in real time by virtue of a limited computational effort, also keep the communication effort to a minimum. In the proposed control scheme, in order to reduce the computational load, the controller updates the control law only when suitable triggering conditions are verified. Moreover, the communication effort is limited since each sensor transmits the measured state to the controller only when a local triggering condition is verified. The simulation tests show that, by applying the proposed control scheme, the computational burden and the communication effort are highly reduced without significantly decreasing the performances of the controlled system.